Plasma cell tumors from man and mouse will be established in tissue culture. These cells will be used as source material for the isolation and characterization of plasma cell antigens. Antigens will be isolated and characterized by means of cell surface labeling followed by reaction with anti-B, T or plasma cell antisera, and the products analyzed by polyacrylamide gel electrophoresis. Antigens will be isolated and characterized by means of potassium chloride extraction gel chromatography, ion exchange chromatography and polyacrylamide gel electrophoresis. The immune response to tumor antigens by peripheral blood leukocytes will be characterized as to the nature of the responding cell and magnitude of the immune response by use of cell separation techniques. Suppressor cell populations for the immune response to plasma cell antigens, immunoglobulin production and mixed lymphocyte reactions will be isolated, their activity quantified and the mechanism of action explored. These studies will involve cell separation techniques, the use of cell surface markers, including heterologous antisera to B, T and plasma cells, cell surface labeling and immunochemical characterization.